Concealing Water Stains On Plaster Surfaces
CONCEALING WATER STAINS ON PLASTER SURFACES
A. This procedure includes guidance on concealing water
stains on plaster walls or ceilings using a shellac-based
primer sealer. A product, such as white-pigmented shellac
can be used to seal, prime and block out existing stains,
prohibiting them from bleeding through finish layers of
B. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
A. Zinsser Brand
B. Kilz, www.kilz.com
A. White-pigmented shellac such as "Kilz" (Kilz),
"Bin" (Rustoleaum), or approved equal. Both are available from hardware
stores in spray cans or brushable liquid.
A. Clean sponge
B. Stiff, fiber bristle brush
C. Paint brush, roller or airless sprayer
A. Before proceeding with steps to conceal water stains,
examine the plaster and substrate material for potential
sources of moisture and make repairs as required. For
guidance on cleaning and/or repairing damaged plaster,
see 09200-01-S, 09210-02-R, 09210-03-R and 09210-05-R.
1. Look for signs of water infiltration: Examination
may show where the water is entering.
2. If possible, examine the condition of the back-up
a. CAREFULLY EXAMINE the wall for open gaps or
cracks in joints and around openings that
could allow water to enter the building.
1) Are joints properly caulked or sealed?
2) Are flashings and drips in good
3) Are there open or eroded mortar joints in
copings or in sills?
b. Carefully note the condition and profile of
the mortar joints.
c. Repair cracks in masonry and/or repoint as
necessary before proceeding with the cleaning
3. Examine wall sections and details of construction:
Carefully examine roof and wall junctures and
flashing details for possible sources of moisture
3.02 ERECTION, INSTALLATION, APPLICATION
A. After source of moisture has been eliminated, allow the
surface to thoroughly dry out.
B. Carefully remove any surface deposits and loose paint
using a stiff fiber bristle brush only. Fill cracks and
holes as required.
C. Wipe the surface with a clean, damp cloth.
D. Apply white-pigmented shellac over the stained area using
a brush, roller or airless sprayer. Follow
1. Depending on the severity of the stain, multiple
coats may be required. If so, allow the first coat
to thoroughly dry (typically 45 minutes) before
proceeding with additional coats.
2. If using a brush or roller, apply additional coats
in the same direction as the first coat.
3. If the surface is to be repainted with a high-
hiding paint, spot-priming only the stained areas
is acceptable. However, if a high-hiding paint is
NOT used to finish the surface, spot-priming is NOT
RECOMMENDED, as primed areas may appear shiny
through the paint finish. (Note: Many ceiling
paints have little hiding strength). In such
cases, the entire wall or ceiling surface should be
primed with the white-pigmented shellac before
repainting to produce a more uniform final
E. Prime and repaint the entire surface with oil or latex
paint as required. For guidance on painting, see 09900-
07-S and 09900-08-S.
END OF SECTION